A #8 wire with an insulation rating of 75 or 90 degrees C is rated at 45 amps.
At the service entrance you will need AWG 1/0 gauge.
A #3 copper wire with an insulation factor 90 degree C is rated at 105 amps.
You would need to use a #12 copper conductor to continuously draw 14 amps at 120 volts.
15 amps
The ampacity of an 8 gauge wire at 240 volts would depend on the specific type of wire and the installation conditions. Generally, an 8 gauge wire can safely carry around 40-50 amps of current. It is important to consult the National Electrical Code (NEC) and local regulations for precise guidance.
A # 14 copper conductor will be fine to carry 8 amps at 120 volts. This size conductor is rated at 15 amps.
AWG # 10.
30 amps.
14 gauge wire is for 15 amp circuits. At 220 volts that would be enough for 2.4 kw.At 120 volts it would need 12 gauge wire which is rated for 20 amps.
A #14 wire will do the job.
140 AMPS
Depends upon the voltage. The formula for amperage or (wire size) is Watts / Voltage. If the voltage is 220 volts, then the amperage would be over 400 amps. This would require a large wire size to run it. If it were 440 volts, the amperage would be 1/2 or 200 amps. That would require a smaller wire size. As the voltage goes up, the amperage goes down. At a thousand volts, the amperage would only be 90 amps. A wire gauge or size of a #2 would carry 90 amps for small distances.